Some heavy rainfall is expected to hit Northern California on...

Some heavy rainfall is expected to hit Northern California on Thursday and Friday.

Hopefully, this should help to dampen the fires that are still threatening homes. It is perhaps not such good news for the almond growers who are trying to complete their harvest, though it will take more than one day of inclement weather to put a dent in the statewide almond crop.

The Californian almond expert David Doll has done an investigation into the high number of almond kernel defects that have been showing up this year, and published the results on his website. He identified four causes primarily responsible for the large number of defects, summarised below:

1. Leaf-footed plant bug damage: there were large numbers of this insect in and around Californian orchards this year as a result of the increased vegetation growth following on from the heavy rainfall earlier in the year.

2. Boron deficiency: Interestingly, during the drought years Californian growers were worrying about excess boron levels impacting their almond trees, so I would guess that the damage from boron deficiency this year may be connected to the heavy rainfall in northern areas of the state.

3. Navel Orangeworm damage: Apparently, this major problem of 2017 was down to a combination of the the heavy rainfall earlier in the year, which prevented farmers in some areas from reaching their orchards to undertake preventative measures; and in addition, the unusually high temperatures in July and August helped to boost the numbers of this pest.

Although not mentioned by David Doll, there have also been some suggestions that the increase in navel orangeworm activity may also be connected to the increasing popularity of the 'Independence' self-pollinating variety of almond tree across California.

4. Staining from a fungus called Aspergillus Niger, which seems to have resulted from high humidity levels.

That last point is interesting, and it is worth considering if fungus damage may have been partly responsible for the poor quality of much of Select's crop earlier this year?.  The heavy rainfall in the company orchards in late 2016 combined with the extreme heat in January and February of this year may have provided a warm, moist environment which would be ideal for the growth of fungi.


Some of the conditions that were faced by Californian growers this year were comparable to those in the almond growing areas of Australia in late 2016/ early 2017.

The original estimate for the Australian crop of 2017 was around 85,000 tonnes, but it came in at 82,333 tonnes, about 2% less. So will the Californian almond estimate also prove to be a little on the high side, given the similar weather conditions?.

One key difference is that the southern areas of California, which typically produces about 40% of the crop of the state, doesn't appear to be quite so severely impacted by the problems mentioned by David Doll. All the same, I think at this stage it is a fair bet that the Californian almond crop is probably not going to meet the forecast.